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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="fusion.container.map"></a><a class="link" href="map.html" title="map">map</a>
</h3></div></div></div>
<h5>
<a name="fusion.container.map.h0"></a>
        <span class="phrase"><a name="fusion.container.map.description"></a></span><a class="link" href="map.html#fusion.container.map.description">Description</a>
      </h5>
<p>
        map is an <a class="link" href="../sequence/concepts/associative_sequence.html" title="Associative Sequence">Associative
        Sequence</a> of heterogeneous typed data elements. Each element is a key/data
        pair (see <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">fusion</span><span class="special">::</span><span class="identifier">pair</span></code></a>)
        where the key has no data (type only). Type identity is used to impose an
        equivalence relation on keys. A map may contain at most one element for each
        key. Membership testing and element key lookup has constant runtime complexity
        (see <a class="link" href="../notes.html#fusion.notes.overloaded_functions">Overloaded Functions</a>).
      </p>
<h5>
<a name="fusion.container.map.h1"></a>
        <span class="phrase"><a name="fusion.container.map.header"></a></span><a class="link" href="map.html#fusion.container.map.header">Header</a>
      </h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">map</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">map</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">map</span><span class="special">/</span><span class="identifier">map_fwd</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">map_fwd</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<h5>
<a name="fusion.container.map.h2"></a>
        <span class="phrase"><a name="fusion.container.map.synopsis"></a></span><a class="link" href="map.html#fusion.container.map.synopsis">Synopsis</a>
      </h5>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span>
    <span class="keyword">typename</span> <span class="identifier">T0</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span>
  <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T1</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span>
  <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T2</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span>
    <span class="special">...</span>
  <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">TN</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span>
<span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">map</span><span class="special">;</span>
</pre>
<p>
        For C++11 compilers, the variadic function interface has no upper bound.
      </p>
<p>
        For C++03 compilers, the variadic class interface accepts <code class="computeroutput"><span class="number">0</span></code>
        to <code class="computeroutput"><span class="identifier">FUSION_MAX_MAP_SIZE</span></code> elements,
        where <code class="computeroutput"><span class="identifier">FUSION_MAX_MAP_SIZE</span></code>
        is a user definable predefined maximum that defaults to <code class="computeroutput"><span class="number">10</span></code>.
        Example:
      </p>
<pre class="programlisting"><span class="identifier">map</span><span class="special">&lt;</span><a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;,</span> <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">char</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;,</span> <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">double</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;</span> <span class="special">&gt;</span>
</pre>
<p>
        You may define the preprocessor constant <code class="computeroutput"><span class="identifier">FUSION_MAX_MAP_SIZE</span></code>
        before including any Fusion header to change the default. Example:
      </p>
<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">FUSION_MAX_MAP_SIZE</span> <span class="number">20</span>
</pre>
<h5>
<a name="fusion.container.map.h3"></a>
        <span class="phrase"><a name="fusion.container.map.template_parameters"></a></span><a class="link" href="map.html#fusion.container.map.template_parameters">Template
        parameters</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Parameter
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
<th>
                <p>
                  Default
                </p>
              </th>
</tr></thead>
<tbody><tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">T0</span></code>...<code class="computeroutput"><span class="identifier">TN</span></code>
                </p>
              </td>
<td>
                <p>
                  Element types
                </p>
              </td>
<td>
                <p>
                  <span class="emphasis"><em>unspecified</em></span>
                </p>
              </td>
</tr></tbody>
</table></div>
<h5>
<a name="fusion.container.map.h4"></a>
        <span class="phrase"><a name="fusion.container.map.model_of"></a></span><a class="link" href="map.html#fusion.container.map.model_of">Model
        of</a>
      </h5>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            <a class="link" href="../sequence/concepts/associative_sequence.html" title="Associative Sequence">Associative
            Sequence</a>
          </li>
<li class="listitem">
            <a class="link" href="../sequence/concepts/random_access_sequence.html" title="Random Access Sequence">Random
            Access Sequence</a>
          </li>
</ul></div>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl class="variablelist">
<dt><span class="term"><code class="computeroutput"><span class="identifier">M</span></code></span></dt>
<dd><p>
              A <code class="computeroutput"><span class="identifier">map</span></code> type
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">m</span></code></span></dt>
<dd><p>
              An instance of <code class="computeroutput"><span class="identifier">map</span></code>
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">e0</span></code>...<code class="computeroutput"><span class="identifier">en</span></code></span></dt>
<dd><p>
              Heterogeneous key/value pairs (see <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">fusion</span><span class="special">::</span><span class="identifier">pair</span></code></a>)
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt>
<dd><p>
              A <a class="link" href="../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
              Sequence</a>
            </p></dd>
</dl>
</div>
<h5>
<a name="fusion.container.map.h5"></a>
        <span class="phrase"><a name="fusion.container.map.expression_semantics"></a></span><a class="link" href="map.html#fusion.container.map.expression_semantics">Expression
        Semantics</a>
      </h5>
<p>
        Semantics of an expression is defined only where it differs from, or is not
        defined in <a class="link" href="../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
        Sequence</a> and <a class="link" href="../sequence/concepts/associative_sequence.html" title="Associative Sequence">Associative
        Sequence</a>.
      </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Expression
                </p>
              </th>
<th>
                <p>
                  Semantics
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">M</span><span class="special">()</span></code>
                </p>
              </td>
<td>
                <p>
                  Creates a map with default constructed elements.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">M</span><span class="special">(</span><span class="identifier">e0</span><span class="special">,</span>
                  <span class="identifier">e1</span><span class="special">,...</span>
                  <span class="identifier">en</span><span class="special">)</span></code>
                </p>
              </td>
<td>
                <p>
                  Creates a map with element pairs <code class="computeroutput"><span class="identifier">e0</span></code>...<code class="computeroutput"><span class="identifier">en</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">M</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code>
                </p>
              </td>
<td>
                <p>
                  Copy constructs a map from a <a class="link" href="../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
                  Sequence</a> <code class="computeroutput"><span class="identifier">s</span></code>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">m</span> <span class="special">=</span>
                  <span class="identifier">s</span></code>
                </p>
              </td>
<td>
                <p>
                  Assigns to a map, <code class="computeroutput"><span class="identifier">m</span></code>,
                  from a <a class="link" href="../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
                  Sequence</a> <code class="computeroutput"><span class="identifier">s</span></code>.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="fusion.container.map.h6"></a>
        <span class="phrase"><a name="fusion.container.map.example"></a></span><a class="link" href="map.html#fusion.container.map.example">Example</a>
      </h5>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">map</span><span class="special">&lt;</span>
    <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;</span>
  <span class="special">,</span> <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="special">&gt;</span>
<span class="identifier">map_type</span><span class="special">;</span>

<span class="identifier">map_type</span> <span class="identifier">m</span><span class="special">(</span>
    <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">make_pair</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="char">'X'</span><span class="special">)</span>
  <span class="special">,</span> <a class="link" href="../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">make_pair</span></code></a><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;(</span><span class="string">"Men"</span><span class="special">));</span>

<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <a class="link" href="../sequence/intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="identifier">m</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <a class="link" href="../sequence/intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;(</span><span class="identifier">m</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman,
      Dan Marsden, Tobias Schwinger<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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